This invention relates to a novel 92-kDA type IV collagenase and a cDNA clone representing the full size protein.
Resident cells of tissues are capable of secreting an array of enzymes initiating the degradation of the surrounding macromolecules of extracellular matrix (ECM), which presumably contributes to the initial steps of tissue remodeling during morphogenesis, wound healing, angiogenesis and tumor invasion. Several of the metalloproteases of this class have been shown to be structurally related and comprise a novel secreted protease gene family, which includes, among other things, collagenase, stromelysin, and a 72-kDA type IV collagenase. The expression of genes coding for these enzymes is cell-type specific, and is regulated by growth factors, oncogenes, mediators of inflammation and tumor promoters. The extracellular activity of these enzymes is modulated by proenzyme activation, interaction with the specific tissue inhibitor of metalloprotease (TIMP), and microenvironmental factors such as tissue localization.
The ECM metalloproteases are secreted as zymogens which undergo extracellular activation. One possible pathway of activation of interstitial collagenase involves a cascade of proteolytic events in which processing of the amino-terminal portion of the enzyme by plasmin results in removal of 84 amino acid residues. A second step requires the presence of plasmin activated stromelysin, which removes approximately 15 residues from the carboxy end of the molecule, resulting in the fully activated enzyme. Interstitial collagenase once activated can form an enzyme inhibitor complex with TIMP. However, no complex formation between the latent procollagenase and TIMP occurs.
The present inventors have previously disclosed in copending application Ser. No. 07/93,421, filed Sept. 4, 1987, that human bronchial epithelial cells secrete a 72-kDa type IV collagenase in response to transformation with the H-ras oncogene. See also Collier et al., J. Biol. Chem. 263, 6579-6587 (1988). The same enzyme is secreted by a variety of tumor cells as well as by normal human skin fibroblasts.